Polyaniline decorated honeycomb-patterned pores: Use of a reactive vapor in breath figure method

Antibacterial Activity of Polyaniline Coated in the Patterned Film Depending on the Surface Morphology and Acidic Dopant

We have fabricated poly(ε-caprolactone) (PCL) films with flat and honeycomb-patterned (HCP) structures to coat polyaniline (PANI) on the film surface. In addition, the effect of chemical modification of PANI by sulfuric acid (H2SO4) was also studied for antibacterial activity. The flat and HCP PCL films were obtained by simple evaporation of the solvent and via the breath figure (BF) method, respectively. The morphology and chemical composition of PANI coated on the film surface were evaluated by scanning electron microscopy (SEM) and X-ray spectroscopy (EDX). Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analyses (TGA) were obtained to identify the PANI coating. The wettability and conductivity of the films were also measured. Applicational aspects were evaluated by assessing antibacterial and antibiofilm activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The EDX, TGA, and FT-IR findings indicated chemical modification of PCL film by PANI and H2SO4. The conductivity of the films was increased by the coating of PANI to the patterned surface and additionally increased by the chemically modified PANI. The antibacterial activity was 69.79%, 78.27%, and 88% against E. coli, and 32.73%, 62.65%, and 87.97% against S. aureus, for flat PANI, HCP PANI, and H2SO4-treated HCP films, respectively. Likewise, the PANI coated flat, HCP, and H2SO4-treated HCP films inhibited E. coli biofilm formation by around 41.62%, 63%, and 83.88% and S. aureus biofilm formation by 17.81%, 69.83%, and 96.57%, respectively. The antibacterial activity of the HCP film was higher than that of flat PANI films, probably due to the higher coating of PANI on the HCP surface. Moreover, sulfonation of the HCP film with H2SO4 might have improved the wettability, thereby enhancing the antibacterial and antibiofilm properties. Our results showed that topographical changes, as well as doping, offer simple and cost-effective ways to modify the structural and functional properties of films.

Modified Breath Figure Methods for the Pore-Selective Functionalization of Honeycomb-Patterned Porous Polymer Films

Recent developments in the field of the breath figure (BF) method have led to renewed interest from researchers in the pore-selective functionalization of honeycomb-patterned (HCP) films. The pore-selective functionalization of the HCP film gives unique properties to the film which can be used for specific applications such as protein recognition, catalysis, selective cell culturing, and drug delivery. There are several comprehensive reviews available for the pore-selective functionalization by the self-assembly process. However, considerable progress in preparation technologies and incorporation of new materials inside the pore surface for exact applications have emerged, thus warranting a review. In this review, we have focused on the pore-selective functionalization of the HCP films by the modified BF method, in which the self-assembly process is accompanied by an interfacial reaction. We review the importance of pore-selective functionalization, its applications, present limitations, and future perspectives.

Hierarchical Nano/Micro Moth Eyelike Polymer Film Using Solid/Liquid Interfacial Reaction at Room Temperature

A simple pathway for the fabrication of real moth eyelike patterned (MEP) polymer film with a double-layered nano/microhierarchical structure is demonstrated through a solid/liquid interfacial reaction at atmospheric conditions. A convex-structured polyvinyl alcohol (PVA) film containing CdCl₂ was first fabricated using a self-organized honeycomb-patterned porous film as a template. The CdCl₂/PVA convex film was immersed into Na₂S/ethanol solution to facilitate the reaction between CdCl₂ and Na₂S at the solid/liquid interface, which led to the functionalization of CdS nanoparticles in the convex-structured PVA film. The tunable introduction of interfacial reaction resulted in the formation of a CdS moth eyelike nanoarray on the top surface of the PVA convex microarray, which mimicked the real moth eye (PVA-CdS MEP). PVA-CdS MEP film with a double moth eyelike structure showed improved antireflective property in comparison with flat and convex-structured PVA films. The PVA-CdS MEP film showed photoresponse under simulated solar light radiation and flexible duration after 500 cycles of folding.